The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 198 41 638.5, filed Sep. 11, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to methods and associated devices for the moisture profiling of a fibrous material web to be dried, and more specifically to the moisture profiling of a paper, cardboard, or tissue web, in machines for manufacturing or refining this web.
2. Discussion of Background Information
Currently, fibrous material webs are guided by a heated cylinder for drying. In this costly process, an uneven distribution of moisture, laterally to the fibrous material web, often sets in. To correct this moisture cross direction profile, particular zones are additionally moistened or heated. The heating generally takes place inductively or by IR radiator(s). The moistening is carried out with steam.
However, these corrective measures are relatively imprecise. Furthermore, the measurement and regulation of the moisture profile is very costly.
Accordingly, the present invention is directed to a method and device for moisture profiling of a fibrous material web to be dried that substantially obviates one or more of the problems arising from the limitations and disadvantages of the related art.
It is an object of the present invention to provide a method and device for moisture profiling that is as simple and precise as possible.
It is a further object of the present invention to provide a method and device for moisture profiling that balances out moisture variances laterally to a fibrous material web.
Accordingly, one aspect of the present invention is directed to a method for moisture profiling of a fibrous material web to be dried in machines for manufacturing and/or refining this web that includes subjecting the fibrous material web to electromagnetic waves in the form of microwaves and/or high-frequency waves.
According to another aspect of the present invention, the field energy of the electromagnetic waves are distributed as evenly as possible laterally to the fibrous material web.
According to yet another aspect of the present invention, the electromagnetic waves are used when there is a dry matter content of the fibrous material web between approximately 60 and 95%.
In a further aspect of the present invention, the fibrous material web travels in a supported manner at least in the vicinity of the electromagnetic waves.
According to another aspect of the present invention, a drying of the fibrous material web may be produced at least predominantly by the electromagnetic waves.
According to yet another aspect of the present invention, the drying of the fibrous material web may be produced only to a small degree by the electromagnetic waves. The drying of the fibrous material web preferably serving to balance out moisture variances laterally to the fibrous material web.
In a further aspect of the present invention, the fibrous material web may be conveyed past at least one microwave transmitter.
According to another aspect of the present invention, the microwave transmitter includes at least one wave guide respectively connected to at least one microwave source.
According to yet another aspect of the present invention, the wave guides are distributed evenly laterally to the fibrous material web.
In a further aspect of the present invention, the fibrous material web may be guided by a rotating cylinder in the vicinity of a microwave transmitter.
According to another aspect of the present invention, the casing of the rotating cylinder and/or an outer cover of this casing may be composed of a material which does not absorb the microwaves as well as the fibrous material web.
According to yet another aspect of the present invention, the thickness of the outer cover may be between approximately 5 and 150 mm.
In a further aspect of the present invention, the thickness of the outer cover may be between approximately 10 and 50 mm.
According to another aspect of the present invention, the travel of the fibrous material web may be supported by at least one wire. The material of the at least one wire not absorbing the microwaves as well as the fibrous material web.
According to yet another aspect of the present invention, the fibrous material web may be conveyed past at least two electrodes of different polarity that are connected to a high-frequency source.
In a further aspect of the present invention, the electrodes have the form of bar electrodes, capacitor plates, and/or rotating cylinders.
According to another aspect of the present invention, the fibrous material web may be guided by a rotating cylinder in the vicinity of the electrodes. The fibrous material web preferably is supported by a wire.
According to yet another aspect of the present invention, the rotating cylinder is preferably embodied predominantly of metal. The rotating cylinder constitutes an electrode and a bar electrode and/or a capacitor plate of a different polarity arranged on the opposite side in relation to the fibrous material web.
In a further aspect of the present invention, the rotating cylinder has an electrically insulating outer cover.
According to another aspect of the present invention, the invention includes at least two bar electrodes of different polarity in the winding region of the rotating cylinder. The high-frequency waves of the at least two bar electrodes partially penetrate the fibrous material web.
According to yet another aspect of the present invention, the device has an electromagnetic shield.
In a further aspect of the present invention the invention is directed to a method for moisture profiling of a fibrous material web to be dried that includes conveying a fibrous material web past at least one electromagnetic wave source. The fibrous material web may be subjected to electromagnetic waves from the at least one electromagnetic wave source. Moister areas of the fibrous material web are dried more intensely than dried areas of the fibrous material web. The drying may be caused by the electromagnetic waves.
According to another aspect of the present invention, the electromagnetic waves include microwaves and/or high-frequency waves.
According to yet another aspect of the present invention, the electromagnetic wave source includes a microwave transmitter and/or at least two electrodes of different polarity connected to a high-frequency source.
In a further aspect of the present invention, the field energy of the electromagnetic waves may be distributed evenly laterally to the fibrous material web. The even distribution produces a uniform drying action on the fibrous material web.
In a still further aspect of the present invention, moisture variances may be balanced out laterally to the fibrous material web by the drying.
According to another aspect of the present invention the invention is directed to a device for moisture profiling of a fibrous material web to be dried in machines for manufacturing and/or refining this web that includes a fibrous material web support that supports travel of the fibrous material web. Also, the device includes a rotating cylinder where the rotating cylinder receives the fibrous material web from the fibrous material web support. The fibrous material web support may be arranged outside the fibrous material web in relation to the surface of the rotating cylinder. The device further includes at least one electromagnetic wave transmitter. The rotating cylinder conveys the fibrous material web past the at least one electromagnetic wave transmitter. The electromagnetic wave transmitter produces electromagnetic waves laterally to the material fibrous web. The electromagnetic waves balance out moisture variances laterally to the fibrous material web by drying moister areas of the fibrous material web more intensely than dried areas of the fibrous material web.
According to yet another aspect of the present invention, the fibrous material web support includes at least one wire whose material does not absorb the electromagnetic waves as well as the fibrous material web.
In a further aspect of the present invention, the rotating cylinder has an outer cover. The outer cover may be composed of a material that does not absorb the electromagnetic waves as well as the fibrous material web.
According to another aspect of the present invention, the outer cover material may be Teflon (polytetrafluorethylene).
According to yet another aspect of the present invention, the at least one electromagnetic wave transmitter includes a microwave transmitter and/or at least two electrodes of different polarity connected to a high-frequency source.
In a further aspect of the present invention, the at least one electromagnetic wave transmitter may be evenly distributed laterally to the fibrous material web.
According to another aspect of the present invention, the at least two electrodes of different polarity connected to a high-frequency source may include bar electrodes, capacitor plates, and/or the rotating cylinder.
According to yet another aspect of the present invention, the microwave transmitter includes an alignment of a plurality of wave guides having a rectangular cross section. The waves guides may be connected to a microwave source and extend laterally to the web travel direction.
In a further aspect of the present invention, the outer cover may be electrically insulating.
According to another aspect of the present invention, the bar electrodes and capacitor plates may be arranged in a winding region of the rotating cylinder and extend essentially laterally to the fibrous material web and parallel to the rotating cylinder.